B153 - Caprine arthritis/encephalitis

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B153 - Caprine arthritis/encephalitis

Nature of the disease
Caprine arthritis/encephalitis (CAE) is a viral disease of goats due to a lentivrus of the Retroviridae family, its is closely related to the Maedi/Visna virus. It is characterised by arthriytis and sometimes encephalitis and pneumonia.
Classification
OIE, List B disease
Susceptible species
Caprine
Distribution
CAE is worldwide distributed. In the Pacific it is present in Australia and in New Zealand, doubtful results were found in Fiji and in French Polynesia. Other countries never reported the disease.
Clinical signs 
Only 30% of infected animals develop a disease. There are three different forms of the disease. 
  • Arthritis or "bigf knee": 
    • Arthtritis mainly visible on the carpal joints, also involve the tarsal joints,
    • Lameness, 
    • Weight loss depsite a normal appetite
    • Poor hair coat,
    • Reduction of milk yield.
  • Mastitis: it is characterised by chronic induration of the udder (hard udder) with reduced milk production. 
  • Encephalitis:
    • Weakness,
    • Coordination disorders, ataxia,
    • Paralysis of hindlimbs,
    • Complete parlaysis in kids between 2 and 4 months.
  • Pneumonia: rare form of intersticial pneumonia
Post-mortem findings 
Lesions may include:
  • Emaciation and chronic polysynovitis,
  • Enlarged lymph nodes at proximity of joints,
  • Diffuse  intersticial pneumonia,
  • bilateral non suppurative demyelinating encephalomyelotis associated with encephalitis form
Differential diagnosis 
  • Arthritis:
    • Defficiency in Vitamin E
    • Septic arthritis,
    • Injury
  • Encephalitis:
    • Scrapie,
    • Listeriosis,
    • Toxoplasmosis
Specimens required for diagnosis 
Usually diagnostic is achieved by serological tests. The prescibed test is agar gel immunodiffusion test but ELISA is also available. There is an antibody assay on milk for dairy goat herds. 

For virus identification samples of wole blood on EDTA or specimens of lung, synovial membranes and udder on Hanks’ balanced salt solution, can, be submitted for culture. PCR is also available.

Transmission   
The pricnipal route of infection is through colostrum. Horizontal and in utero infections are possible but rare.
Risk of introduction   
Risk of introduction of CAE is through importation of live infected animals. Inaparent carriers from infected zones are particularly risky. 
Control / vaccines  
There is no vaccine. Control can be achieved by segregation of sick animals and progressive removal.
References
  • Caprine arthritis/encephalitis, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 523-526
  • Caprine arthritis/encephalitis, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 1110-1112
  • Office International des Epizooties, 2002
  • Office Vétérinaire Fédéral Suisse